Laser oscillation apparatus, exposure apparatus, semiconductor device manufacturing method, semiconductor manufacturing factory, and exposure apparatus maintenance method

ABSTRACT

A laser oscillation apparatus includes a wavelength change unit for driving a wavelength selection element in a band-narrowing module and changing the oscillation wavelength of a laser beam to a target value, and an oscillation history memory for storing the oscillation state of the laser beam as an oscillation history. The wavelength change unit drives the wavelength selection element on the basis of the oscillation history and changes the oscillation wavelength of the laser beam to the target value.

FIELD OF THE INVENTION

[0001] The present invention relates to a laser oscillation apparatuscapable of changing the oscillation wavelength of, e.g., a laser beam,an exposure apparatus using the same, a semiconductor devicemanufacturing method, a semiconductor manufacturing factory, and anexposure apparatus maintenance method.

BACKGROUND OF THE INVENTION

[0002] Step & repeat type or step & scan type exposure apparatuses playa dominant role in the semiconductor integrated circuit manufacturingprocess. Such an exposure apparatus exposes the surface of a substrate(to be referred to as a wafer hereinafter) coated with a resist to thecircuit pattern of a mask or reticle (to be referred to as a reticlehereinafter) via a projection lens. Recently, the integration degree ofsemiconductor integrated circuits is increasing. Along with this,demands have arisen for a light source for emitting exposure lighthaving a shorter wavelength. In particular, a rare gas hydride excimerlaser (to be referred to as an excimer laser hereinafter) as a kind oflaser oscillation apparatus is receiving a great deal of attention as anultraviolet high-output laser.

[0003] An exposure apparatus is generally used in a clean room. As theatmospheric pressure in the clean room changes upon changes in weather,the refractive index of exposure light changes, and the imaging positionof a circuit pattern varies. In general, an excimer laser for theexposure apparatus can change the oscillation wavelength within therange of about 300 to 400 pm. The refractive index of exposure lightchanges depending on the wavelength. For this reason, the atmosphericpressure in the use environment of the exposure apparatus is measured ata proper timing such as the start of a job or exchange of a wafer, anoptimal oscillation wavelength which should be oscillated to cancelvariations in imaging position caused by a change in atmosphericpressure is calculated, and the oscillation wavelength of the excimerlaser is changed by a desired amount. In this manner, the exposureapparatus copes with a change in atmospheric pressure in the useenvironment of the exposure apparatus.

[0004] This exposure apparatus performs exposure by a processing flow asshown in FIG. 12.

[0005] After the start of a job (step 901), the atmospheric pressurenear the projection lens is measured at a proper timing such as a waferloading timing (step 902). The main controller of the exposure apparatuscalculates an oscillation wavelength (target oscillation wavelengthvalue) optimal for exposure on the basis of the atmospheric pressure(step 903). The target oscillation wavelength value is transmitted to anexcimer laser controller (step 904). An excimer laser oscillationapparatus closes a shutter arranged at an excimer laser exit port (step905). The excimer laser controller emits a test excimer beam whileoscillating a pulse beam, and adjusts the oscillation wavelength withina predetermined allowable range by using a wavelength change means whilemonitoring the oscillation wavelength by using the internal opticalmeasurement unit of the excimer laser oscillation apparatus (step 906).

[0006] The laser oscillation apparatus checks whether the oscillationwavelength falls within a predetermined allowable range of apredetermined target oscillation wavelength value (step 907). If NO instep 907, the excimer laser changes to an error state and stopsoscillation (step 908). If YES in step 907, the laser oscillationapparatus transmits a wavelength lock signal “ON” representing this tothe exposure apparatus, opens the shutter (step 909), and startsexposure in accordance with an emission signal from the exposureapparatus (step 910). After exposure, the wafer is unloaded (step 911),and whether to expose the next wafer is determined (step 912). If NO instep 912, the job ends (step 913); if YES, the flow returns to step 902.

[0007] In the prior art, every time the oscillation wavelength ischanged, the shutter must be closed to emit a test laser beam in orderto confirm whether the changed oscillation wavelength reaches a targetvalue. Shutter opening/closing operation and test emission decrease theproductivity of the exposure apparatus.

SUMMARY OF THE INVENTION

[0008] The present invention has been made in consideration of the abovesituation, and has as its object to provide an exposure apparatus foralways exposing a wafer to a circuit pattern with high precision withoutdecreasing the productivity of the exposure apparatus when a laseroscillation apparatus is used as the light source of the exposureapparatus, a semiconductor device manufacturing method, a semiconductormanufacturing factory, and an exposure apparatus maintenance method.

[0009] To achieve the above object, according to the present invention,a laser oscillation apparatus is characterized by comprising wavelengthchange means for driving a wavelength selection element and changing anoscillation wavelength of a laser beam to a target value, wherein thewavelength change means calculates a driving amount of the wavelengthselection element on the basis of the target value, drives thewavelength selection element on the basis of the calculated drivingamount of the wavelength selection element, and changes the oscillationwavelength of the laser beam to the target value. The wavelength changemeans desirably calculates the driving amount of the wavelengthselection element on the basis of an oscillation history, drives thewavelength selection element on the basis of the calculated drivingamount of the wavelength selection element, and changes the oscillationwavelength of the laser beam to the target value. The wavelengthselection element desirably includes one of a grating and etalon.

[0010] According to the experiments by the present inventors, thewavelength of a laser beam is unstable and drifts immediately after thestart of laser oscillation or at several ten to several hundred pulsesfrom the start of a burst in burst oscillation, and the drift amountchanges depending on the laser oscillation history or the internalenvironment of a wavelength measurement unit in a laser oscillationapparatus. The oscillation history includes the wavelength change width,the lapse time after the stop of oscillation, and the oscillation duty(the ratio of oscillation time/idle time). The internal environment ofthe wavelength measurement unit includes the atmospheric pressure andtemperature. A laser oscillation apparatus of the present invention morepreferably incorporates one or both of an oscillation history memorymeans for storing the oscillation history of a laser beam and aninternal wavelength measurement unit environment measurement means formeasuring the internal environment of the wavelength measurement unit.The drift amount of the wavelength measurement unit in the laseroscillation apparatus is calculated by using at least one of theoscillation history stored in the oscillation history memory means andthe measurement result of the internal wavelength measurement unitenvironment measurement means. A wavelength adjustment means ispreferably driven and controlled in consideration of the calculationresult so as to oscillate a laser beam with a wavelength falling withina predetermined allowable range of a target wavelength.

[0011] It is difficult to adjust the wavelength immediately after thestart of oscillation to a desired range when the laser oscillation idletime is long or the wavelength change amount is very large. It may alsobecome difficult to determine whether the laser oscillation apparatusnormally oscillates a laser beam with a desired allowable range. Thus, adesirable form of the laser oscillation apparatus according to thepresent invention adopts a wavelength lock signal transmission functionof transmitting a signal used to determine whether the oscillationwavelength falls within a predetermined allowable range. A threshold isset for one or both of the oscillation wavelength change amount and thelapse time after the stop of oscillation. The state of the wavelengthlock signal is determined based on the threshold.

[0012] An exposure apparatus according to the present invention uses thelaser oscillation apparatus of the present invention as a light source,and starts exposure without executing test emission for confirmingwhether the wavelength falls within a predetermined allowable range. Ifthe wavelength change amount is very large or the oscillation idle timeis very long or if the wavelength does not fall within the predeterminedallowable range due to any reason, the laser oscillation apparatusoutputs a wavelength lock signal used to determine whether thewavelength is adjusted to the predetermined range. The exposureapparatus determines based on the wavelength lock signal whether toperform test emission by the gas laser oscillation apparatus. Theexposure apparatus of the present invention may change the wavelengthnot only in exchange of one wafer but between the end of exposure to agiven exposure region and the start of exposure to the next exposureregion.

[0013] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a view showing an embodiment of an exposure apparatusaccording to the present invention;

[0015]FIG. 2 is a view showing an embodiment of a laser oscillationapparatus according to the present invention;

[0016]FIG. 3A is a view showing the experimental results of oscillationwavelength stability in the laser oscillation apparatus when theoscillation idle time is changed;

[0017]FIG. 3B is a view showing the experimental results of oscillationwavelength stability in the laser oscillation apparatus when theoscillation idle time is fixed and the oscillation duty is changed;

[0018]FIG. 3C is a view showing the experimental results of oscillationwavelength stability in the laser oscillation apparatus when theoscillation wavelength change amount is changed;

[0019]FIG. 3D is a view showing oscillation wavelength stability in thelaser oscillation apparatus according to the present invention;

[0020]FIG. 4 is a graph showing an example of the wavelength erroramount at the start of laser oscillation depending on the oscillationwavelength change amount;

[0021]FIG. 5 is a flow chart showing a processing flow from the start tothe end of a job by the exposure apparatus according to the presentinvention;

[0022]FIG. 6 is a flow chart showing a processing flow when theoscillation wavelength is changed between the end of exposure to apredetermined exposure region on a wafer and the start of exposure tothe next exposure region by the exposure apparatus according to thepresent invention;

[0023]FIG. 7 is a view showing the concept of a semiconductor deviceproduction system using the apparatus according to the present inventionwhen viewed from a given angle;

[0024]FIG. 8 is a view showing the concept of the semiconductor deviceproduction system using the apparatus according to the present inventionwhen viewed from another angle;

[0025]FIG. 9 is a view showing an example of a user interface;

[0026]FIG. 10 is a flow chart for explaining the processing flow of adevice manufacturing process;

[0027]FIG. 11 is a flow chart for explaining a wafer process; and

[0028]FIG. 12 is a flow chart showing a conventional flow from the startto the end of a job.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Preferred embodiments of the present invention will be describedin detail below with reference to the accompanying drawings.

[0030]FIG. 1 is a view showing an embodiment of an exposure apparatusaccording to the present invention. In FIG. 1, reference numeral 1denotes a known step & repeat (or step & scan) type exposure apparatusmain body generally called a stepper (or scanner); and 2, a laser sourceusing an excimer laser. Examples of the excimer laser are a KrF(wavelength: 248 nm) excimer laser and an ArF (wavelength: 193 nm)excimer laser.

[0031] The exposure apparatus main body 1 is constituted by a beamshaping optical system 3 for shaping the section of a laser beam emittedby the laser source 2 into a desired shape along the optical path of thelaser beam extending from the laser source 2, a variable ND filter 4 foradjusting the intensity of the laser beam, an optical integrator 5 forsplitting the laser beam and superposing the split laser beams in orderto make the illuminance on the surface of a reticle 12 uniform, acondenser lens 6 for condensing the laser beams having passed throughthe optical integrator 5, a beam splitter 7 for guiding some of thelaser beams from the condenser lens 6 to a photodetector 8, a maskingblade 9 which is arranged near a position where the laser beams arecondensed by the condenser lens 6 and regulates the irradiation range ofthe laser beam on the surface of the reticle 12, an imaging lens 10 forforming an image of the masking blade 9 onto the reticle 12, and amirror 11 for deflecting the optical path of the laser beam toward aprojection lens 13.

[0032] The reticle 12 is illuminated with a laser beam which has beenemitted by the laser source 2 and has passed through an illuminationoptical system including these optical elements. A pattern on thereticle 12 is reduced to, e.g., ½ to {fraction (1/10)} and projected(transferred) to one of a plurality of shot regions on a wafer 14serving as a substrate via the projection lens 13 serving as aprojection optical system. The wafer 14 is two-dimensionally moved alonga plane perpendicular to the optical axis of the projection lens 13 by amoving stage (not shown). Every time exposure of an exposure shot regionends, the next exposure shot region is moved to a position where thepattern of the reticle 12 is projected via the projection lens 13.

[0033] Reference numeral 15 denotes a barometer for measuring theatmospheric pressure in the exposure apparatus at a predetermined timeinterval. The measurement value is transmitted to a main controller 16of the exposure apparatus main body 1. The main controller 16 calculatesan optimal oscillation wavelength of a laser beam (target oscillationwavelength value), and transmits a target oscillation wavelength valuesignal to the laser source 2 at a timing between, e.g., the end ofexposure in a predetermined exposure region and the start of exposure inthe next exposure region. The main controller 16 transmits a triggersignal for causing the laser source 2 to emit light. At the same time,the main controller 16 performs photoelectric conversion processing inaccordance with the intensity of the laser beam detected by thephotodetector 8, integrates the result to obtain an exposure amountcontrol signal, and transmits the exposure amount control signal to thelaser source 2. The laser source 2 controls its internal units on thebasis of the target oscillation wavelength value signal, trigger signal,and exposure amount control signal.

[0034] The laser source 2 transmits a wavelength lock signal to the maincontroller 16. This signal is ON when an actual oscillation wavelengthfalls within a predetermined allowable range of a target oscillationwavelength value, and otherwise OFF. When the wavelength lock signal isON, the oscillation wavelength falls within the predetermined allowablerange of the target value, and thus wafer exposure can immediately startwithout opening/closing operation of a shutter in the laser source 2 ortest emission. When the wavelength lock signal is OFF, the maincontroller 16 does not expose the wafer 14, closes the shutter arrangedat the exit port of the laser source 2, and performs test emission inorder to make the oscillation wavelength fall within the predeterminedallowable range. After the oscillation wavelength falls within thepredetermined allowable range, the main controller 16 can open theshutter to start exposure again.

[0035]FIG. 2 is a view showing the schematic internal arrangement of anexcimer laser oscillation apparatus serving as an example of the lasersource 2 shown in FIG. 1.

[0036] The target oscillation wavelength value signal, trigger signal,and exposure amount control signal transmitted from the main controller16 of the exposure apparatus main body 1 are received by a lasercontroller 201. The laser controller 201 transmits a high-voltage signalto a high-voltage power supply 202, and transmits the trigger signal toa compression circuit 203 at a laser emission timing. The lasercontroller 201 transmits the target oscillation wavelength value signalto a wavelength controller 204. A laser chamber 205 incorporatesdischarge electrodes 205A and 205B. A high voltage of about 10 to 30 kVapplied by the compression circuit 203 generates discharge between thedischarge electrodes 205A and 205B to excite a laser gas sealed in thelaser chamber 205, thereby oscillating a laser beam. An output mirror(not shown) is attached to the light exit portion of the laser chamber205. The laser beam oscillated by the laser chamber 205 emerges to thebeam shaping optical system 3 shown in FIG. 1 through a beam splitter206 and shutter 207. Some components of the laser beam are reflected bythe beam splitter 206 and guided to a light monitoring unit 208. Thelaser controller 201 opens/closes the shutter 207 in accordance withinstructions from the main controller 16 in FIG. 1.

[0037] The light monitoring unit 208 always monitors the pulse energyand oscillation wavelength of the laser beam, and determines whether themeasured pulse energy is a desired value with respect to the targetexposure amount value. If the pulse energy is lower than the desiredvalue, the laser controller 201 transmits to the high-voltage powersupply circuit 202 a signal for increasing the application voltage tothe discharge electrodes 205A and 205B, and if the pulse energy ishigher, a signal for decreasing the application voltage. The wavelengthcontroller 204 compares the target oscillation wavelength valuetransmitted from the laser controller 201 with an oscillation wavelengthmeasured by the light monitoring unit 208, and checks whether themeasured oscillation wavelength falls within a predetermined allowablerange of the target oscillation wavelength value. If the oscillationwavelength falls within the predetermined allowable range, waferexposure can immediately start without opening/closing operation of theshutter 207 or test emission. If the oscillation wavelength fallsoutside the predetermined allowable range, the wavelength controller 204transmits a wavelength lock signal “OFF” to the main controller 16 inFIG. 1 via the laser controller 201. If the oscillation wavelength stillfalls outside the target value, the shutter 207 is closed, and thewavelength controller 204 transmits a signal for adjusting thewavelength to fall within the predetermined range to a stepping motor212. When the oscillation wavelength falls within the predeterminedallowable range of the target oscillation wavelength value, thewavelength controller 204 transmits a wavelength lock signal “ON” to themain controller 16 shown in FIG. 1 via the laser controller 201. Then,the shutter 207 is opened.

[0038] The light monitoring unit 208 incorporates an internal lightmonitoring unit environment measurement unit 210 such as a barometer orthermometer for measuring the internal environment of the lightmonitoring unit 208. The refractive index of a laser beam or the like inthe internal environment of the light monitoring unit 208 can becalculated based on the measurement result. The drift amount of thelight monitoring unit 208 can be calculated based on the result andcorrected to always output a laser beam having a stable oscillationwavelength.

[0039] A band-narrowing module 211 is paired with the output mirror (notshown) attached to the light exit portion of the laser chamber 205,thereby constituting a laser resonator. The band-narrowing module 211narrows the spectral line width of a laser beam to about 1 pm as a fullwidth at half maximum. Further, the attached stepping motor 212 isdriven to drive a wavelength selection element such as a grating oretalon incorporated in the band-narrowing module 211, thus changing theoscillation wavelength. At this time, the driving amount of thewavelength selection element is calculated based on the targetoscillation wavelength value. The wavelength controller 204 compares thetarget oscillation wavelength value transmitted from the lasercontroller 201 with an oscillation wavelength measured by the lightmonitoring unit 208, and always controls the oscillation wavelengthwhile transmitting a signal to the stepping motor 212 so as to make theoscillation wavelength of the laser beam fall within a predeterminedallowable range. When the target oscillation wavelength value of theoscillation wavelength is changed again, the wavelength controller 204drives the stepping motor 212 again so as to make the oscillationwavelength coincide with the changed target oscillation wavelengthvalue. To change the oscillation wavelength again, the wavelengthcontroller 204 more preferably predicts and calculates the drift amountof the oscillation wavelength of a laser beam to be oscillated next, onthe basis of an oscillation history stored in an oscillation historymemory 209, and drives the stepping motor 212 on the basis of thecalculation result.

[0040] The experimental results of the oscillation wavelength stabilityof the excimer laser oscillation apparatus by the present inventors willbe described.

[0041]FIG. 3A shows data representing oscillation wavelength stabilityfor oscillation idle times a and b (a<b) between the end of oscillationand the restart of oscillation. For the longer oscillation idle time b,the error amount with respect to the target oscillation value is largerbetween restart of oscillation after the idle time and oscillation ofseveral ten pulses.

[0042]FIG. 3B shows data representing oscillation wavelength stabilityat oscillation duties c and d (c<d) before an idle time when theoscillation idle time is constant between the end of oscillation and therestart of oscillation. For the higher oscillation duty d before theidle time, the error amount with respect to the target oscillation valueis larger between the restart of oscillation after the idle time andoscillation of several ten pulses.

[0043]FIG. 3C shows data representing oscillation wavelength stabilityat oscillation wavelength change amounts e and f (e<f) when oscillationrestarts after the end of oscillation. For the larger oscillationwavelength change amount f, the error amount with respect to the targetoscillation value is larger immediately after oscillation restarts afterthe idle time.

[0044] In this manner, oscillation wavelength stability immediatelyafter oscillation of a laser beam starts is unstable. Drifts of awavelength error called chirping occur at several ten to several hundredpulses from the start of a burst in accordance with the oscillation idletime, oscillation duty, and oscillation wavelength change amount.

[0045] In the present invention, the laser controller 201 or wavelengthcontroller 204 predicts and calculates an oscillation wavelength erroramount (drift amount) generated at the start of a burst, as shown inFIGS. 3A, 3B, and 3C, and corrects and controls the stepping motor 212so as to cancel the drift amount and always oscillate the laser beamwith a desired oscillation wavelength.

[0046] An example of prediction/calculation of the oscillationwavelength drift amount can be approximately given by

Δλ=F(λexc.)+A(1−exp(−Bt))+C+D  (1)

[0047] where Δλ: oscillation wavelength drift amount

[0048] F(λexc.): wavelength amount error dependent on the oscillationwavelength change amount

[0049] A, B: coefficients (dependent on the oscillation duty andoscillation wavelength)

[0050] t: oscillation idle time

[0051] C: chirping

[0052] D: drift amount of the light monitoring unit

[0053] In general, F(λexc.) in equation (1) has a larger value for alarger oscillation wavelength change amount λexc., as shown in FIG. 4.Chirping depends on the internal design of the laser chamber 205. Duringthe manufacturing process of a laser oscillation apparatus, theoscillation wavelength drift amount is experimentally obtained, andF(λexc.), A, B, and C in equation (1) are determined and stored asparameters in the oscillation history memory 209. The refractive indexof a laser beam in the internal environment of the light monitoring unit208 is calculated based on the measurement result of the internal lightmonitoring unit environment measurement unit 210 such as a barometer orthermometer, and the drift amount D of the light monitoring unit 208 isused by using the calculation result. The oscillation wavelength driftamount Δλ is calculated from equation (1) by using these parameters. Thewavelength controller 204 drives the stepping motor 212 so as to makethe oscillation wavelength fall within a predetermined allowable rangefrom the start of a burst, and changes the oscillation wavelength to atarget oscillation wavelength value.

[0054] Letting a (pm/pulse) be an oscillation wavelength change amountwhen one pulse is transmitted to the stepping motor 212, a laser beamcan always oscillate with a wavelength falling within a desiredallowable range by transmitting Δλ/a (pulses) from the wavelengthcontroller 204 to the stepping motor 212 in order to make theoscillation wavelength always fall within the desired allowable range.The step of calculating the oscillation wavelength drift amount Δλ maybe periodically performed when no exposure is done during the operationof the exposure apparatus.

[0055] The experiments by the present inventors show that the wavelengthdrift amount Δλ is larger for a longer idle time after the end ofoscillation. If the oscillation idle time is longer than a given time,the oscillation wavelength of a laser beam immediately after the startof oscillation is difficult to control within a predetermined allowablerange, and desired exposure performance may not be achieved. To preventthis, thresholds are set for the values F(λexc.) and osillation idletime t in equation (1) in the laser controller 201 or wavelengthcontroller 204. If F(λexc.) or osillation idle time t is larger than thethreshold, a wavelength lock signal “OFF” is transmitted. If F(λexc.) ort is smaller than the threshold, the wavelength lock signal is kept“ON”, and exposure operation is possible while the shutter 207 is keptopen.

[0056] For the wavelength lock signal “OFF”, the main controller 16 ofthe exposure apparatus closes the shutter 207 in the laser source 2.While emitting a test laser beam, the laser controller 201 of the lasersource 2 drives the stepping motor 212 and adjusts the oscillationwavelength so as to make the oscillation wavelength fall within apredetermined allowable range. When the oscillation wavelength fallswithin the predetermined allowable range, the laser controller 201transmits a wavelength lock signal “ON” to the main controller 16, whichopens the shutter 207 and outputs a laser beam to the outside of thelaser source 2. FIG. 3D is a view showing a state in which a laser beamcan oscillate with a desired oscillation wavelength even at the start ofa burst as a result of using the above control.

[0057] A processing flow in the exposure apparatus according to thepresent invention will be explained with reference to FIG. 5.

[0058] A job of the exposure apparatus starts (step 501), and thebarometer 15 measures the atmospheric pressure at a wafer loading timing(step 502). The main controller 16 calculates a target oscillationwavelength value (step 503), and transmits it to the laser source 2(step 504). The laser controller 201 of the laser source 2 calculates anoscillation wavelength change amount (step 505), drives the steppingmotor 212 without emitting any test laser beam, and adjusts thewavelength selection element such as a grating or etalon in the bandnarrowing module 211 so as to oscillate the laser beam with a desiredoscillation wavelength (step 506).

[0059] Whether the oscillation wavelength change amount or laser beamoscillation idle time does not exceed its threshold is checked (step507). If NO in step 507, exposure immediately starts withoutopening/closing operation of the shutter 207 or test emission.

[0060] If YES in step 507, a wavelength lock signal “OFF” is transmitted(step 508), the shutter 207 is closed, and the oscillation wavelength isadjusted to fall within an allowable range of the target value while atest laser beam is emitted (step 509). If the oscillation wavelengthfalls within the allowable range, the laser controller 201 transmits awavelength lock signal “ON” to the main controller 16 of the exposureapparatus, which opens the shutter 207 (step 510). Exposure starts inresponse to a trigger signal from the main controller 16 of the exposureapparatus main body (step 512).

[0061] If the oscillation wavelength does not fall within the allowablerange in step 509, the laser oscillation apparatus changes to an errorstate and stops (step 511).

[0062] After wafer exposure ends and the wafer is unloaded (step 513),whether to subsequently expose the next wafer is determined (step 514).If the next wafer is to be exposed, the flow returns to step 502. If NOin step 514, the job ends (step 515).

[0063] In this example, the oscillation wavelength is changed at thewafer loading timing. Alternatively, the oscillation wavelength may bechanged between the end of exposure to a predetermined exposure regionon a wafer and the start of exposure to the next exposure region. Aprocessing flow at this time will be explained with reference to FIG. 6.

[0064] Wafer exposure starts (step 601), and exposure to a givenexposure region starts (step 602). During exposure, the wavelengthcontroller 204 of the laser source 2 always monitors whether theoscillation wavelength stability or error (difference between an actualoscillation wavelength and a target oscillation wavelength value) of anactually oscillated laser beam falls within a predetermined allowablerange (step 603). As far as the oscillation wavelength stability orerror falls within the allowable range, exposure continues (step 604).

[0065] If the oscillation wavelength becomes unstable and does not fallwithin the predetermined allowable range, a wavelength lock signal “OFF”is transmitted to interrupt exposure (step 605). The shutter 207 of thelaser source 2 is closed, and the oscillation wavelength is adjusted tofall within the allowable range while a test laser beam is emitted (step606). If the oscillation wavelength falls within the allowable range, awavelength lock signal “ON” is transmitted in step 607, and exposurerestarts (step 604). If the wavelength cannot be adjusted to fall withinthe allowable range in step 606, the laser source 2 changes to an errorstate and stops exposure (step 608).

[0066] After exposure of a certain exposure region is completed (step609), the main controller 16 of the exposure apparatus determineswhether to expose the next exposure region (step 610). If YES in step610, the main controller 16 calculates a new target oscillationwavelength value from the measurement result of the barometer 15 in step612, and transmits it to the laser source 2. The flow returns to step602, and exposure to the next exposure region starts without emittingany test laser beam. If NO in step 610, wafer exposure ends (step 611),and the wafer is unloaded.

[0067] In this way, the oscillation wavelength of a laser beam ischanged between the end of exposure to a predetermined exposure regionon a wafer and the start of exposure to the next exposure region. Thiscan solve the problem that all exposure regions on a wafer cannot beexposed with an optimal oscillation wavelength owing to an increase inexposure time per wafer along with a recent trend of increasing thewafer diameter.

Embodiment of Semiconductor Production System

[0068] A production system for a semiconductor device (semiconductorchip such as an IC or LSI, liquid crystal panel, CCD, thin-film magnetichead, micromachine, or the like) using the apparatus according to thepresent invention will be exemplified. A trouble remedy or periodicmaintenance of a manufacturing apparatus installed in a semiconductormanufacturing factory, or maintenance service such as softwaredistribution is performed by using a computer network outside themanufacturing factory.

[0069]FIG. 7 shows the overall system cut out at a given angle. In FIG.7, reference numeral 101 denotes a business office of a vendor(apparatus supply manufacturer) which provides a semiconductor devicemanufacturing apparatus. Assumed examples of the manufacturing apparatusare semiconductor manufacturing apparatuses for various processes usedin a semiconductor manufacturing factory, such as pre-processapparatuses (lithography apparatus including an exposure apparatus,resist processing apparatus, and etching apparatus, annealing apparatus,film formation apparatus, planarization apparatus, and the like) andpost-process apparatuses (assembly apparatus, inspection apparatus, andthe like). The business office 101 comprises a host management system108 for providing a maintenance database for the manufacturingapparatus, a plurality of operation terminal computers 110, and a LAN(Local Area Network) 109 which connects the host management system 108and computers 110 to build an intranet. The host management system 108has a gateway for connecting the LAN 109 to Internet 105 as an externalnetwork of the business office, and a security function for limitingexternal accesses.

[0070] Reference numerals 102 to 104 denote manufacturing factories ofthe semiconductor manufacturer as users of manufacturing apparatuses.The manufacturing factories 102 to 104 may belong to differentmanufacturers or the same manufacturer (pre-process factory,post-process factory, and the like). Each of the factories 102 to 104 isequipped with a plurality of manufacturing apparatuses 106, a LAN (LocalArea Network) 111 which connects these apparatuses 106 to build anintranet, and a host management system 107 serving as a monitoringapparatus for monitoring the operation status of each manufacturingapparatus 106. The host management system 107 in each of the factories102 to 104 has a gateway for connecting the LAN 111 in the factory tothe Internet 105 as an external network of the factory.

[0071] Each factory can access the host management system 108 of thevendor 101 from the LAN 111 via the Internet 105. The security functionof the host management system 108 authorizes access of only a limiteduser. More specifically, the factory notifies the vendor via theInternet 105 of status information (e.g., the symptom of a manufacturingapparatus in trouble) representing the operation status of eachmanufacturing apparatus 106, and receives response information (e.g.,information designating a remedy against the trouble, or remedy softwareor data) corresponding to the notification, or maintenance informationsuch as the latest software or help information.

[0072] Data communication between the factories 102 to 104 and thevendor 101 and data communication via the LAN 111 in each factory adopta communication protocol (TCP/IP) generally used in the Internet.Instead of using the Internet as an external network of the factory, adedicated network (e.g., ISDN) having high security which inhibitsaccess of a third party can be adopted. Also the user may construct adatabase in addition to the one provided by the vendor and set thedatabase on an external network, and the host management system mayauthorize access to the database from a plurality of user factories.

[0073]FIG. 8 is a view showing the concept of the overall system of thisembodiment that is cut out at a different angle from FIG. 7. In theabove example, a plurality of user factories having manufacturingapparatuses and the management system of the manufacturing apparatusvendor are connected via an external network, and production managementof each factory or information of at least one manufacturing apparatusis communicated via the external network. In the example of FIG. 8, afactory having manufacturing apparatuses of a plurality of vendors andthe management systems of the vendors for these manufacturingapparatuses are connected via the external network of the factory, andmaintenance information of each manufacturing apparatus is communicated.

[0074] In FIG. 8, reference numeral 301 denotes a manufacturing factoryof a manufacturing apparatus user (semiconductor device manufacturer)where manufacturing apparatuses for various processes, e.g., an exposureapparatus 302, resist processing apparatus 303, and film formationapparatus 304 are installed in the manufacturing line of the factory.FIG. 8 shows only one manufacturing factory 301, but a plurality offactories are networked in practice. The respective apparatuses in thefactory are connected to a LAN 306 to build an intranet, and a hostmanagement system 305 manages the operation of the manufacturing line.

[0075] The business offices of vendors (apparatus supply manufacturers)such as an exposure apparatus manufacturer 310, resist processingapparatus manufacturer 320, and film formation apparatus manufacturer330 comprise host management systems 311, 321, and 331 for executingremote maintenance for the supplied apparatuses. Each host managementsystem has a maintenance database and a gateway for an external network,as described above. The host management system 305 for managing theapparatuses in the manufacturing factory of the user, and the managementsystems 311, 321, and 331 of the vendors for the respective apparatusesare connected via the Internet or dedicated network serving as anexternal network 300. If a trouble occurs in any one of a series ofmanufacturing apparatuses along the manufacturing line in this system,the operation of the manufacturing line stops. This trouble can bequickly solved by remote maintenance from the vendor of the apparatus introuble via the Internet 300. This can minimize the stop of themanufacturing line.

[0076] Each manufacturing apparatus in the semiconductor manufacturingfactory comprises a display, a network interface, and a computer forexecuting network access software and apparatus operating software whichare stored in a storage device.

[0077] The storage device is a built-in memory, hard disk, or networkfile server. The network access software includes a dedicated orgeneral-purpose web browser, and provides a user interface having awindow as shown in FIG. 9 on the display. While referring to thiswindow, the operator who manages manufacturing apparatuses in eachfactory inputs, in input items on the windows, pieces of informationsuch as the type of manufacturing apparatus 401, serial number 402,subject of trouble 403, occurrence date 404, degree of urgency 405,symptom 406, remedy 407, and progress 408.

[0078] The pieces of input information are transmitted to themaintenance database via the Internet, and appropriate maintenanceinformation is sent back from the maintenance database and displayed onthe display. The user interface provided by the web browser realizeshyperlink functions 410 to 412, as shown in FIG. 9. This allows theoperator to access detailed information of each item, receive thelatest-version software to be used for a manufacturing apparatus from asoftware library provided by a vendor, and receive an operation guide(help information) as a reference for the operator in the factory.Maintenance information provided by the maintenance database alsoincludes information concerning the present invention described above.The software library also provides the latest software for implementingthe present invention.

[0079] A semiconductor device manufacturing process using theabove-described production system will be explained. FIG. 10 shows theflow of the whole manufacturing process of the semiconductor device. Instep 1 (circuit design), a semiconductor device circuit is designed. Instep 2 (mask formation), a mask having the designed circuit pattern isformed. In step 3 (wafer manufacture), a wafer is manufactured by usinga material such as silicon. In step 4 (wafer process) called apre-process, an actual circuit is formed on the wafer by lithographyusing a prepared mask and the wafer. Step 5 (assembly) called apost-process is the step of forming a semiconductor chip by using thewafer manufactured in step 4, and includes an assembly process (dicingand bonding) and packaging process (chip encapsulation). In step 6(inspection), inspections such as the operation confirmation test anddurability test of the semiconductor device manufactured in step 5 areconducted. After these steps, the semiconductor device is completed andshipped (step 7). For example, the pre-process and post-process areperformed in separate dedicated factories, and maintenance is done foreach of the factories by the above-described remote maintenance system.Information for production management and apparatus maintenance iscommunicated between the pre-process factory and the post-processfactory via the Internet or dedicated network.

[0080]FIG. 11 shows the detailed flow of the wafer process. In step 11(oxidation), the wafer surface is oxidized. In step 12 (CVD), aninsulating film is formed on the wafer surface. In step 13 (electrodeformation), an electrode is formed on the wafer by vapor deposition. Instep 14 (ion implantation), ions are implanted in the wafer.

[0081] In step 15 (resist processing), a photosensitive agent is appliedto the wafer. In step 16 (exposure), the above-mentioned exposureapparatus exposes the wafer to the circuit pattern of a mask. In step 17(developing), the exposed wafer is developed. In step 18 (etching), theresist is etched except for the developed resist image. In step 19(resist removal), an unnecessary resist after etching is removed. Thesesteps are repeated to form multiple circuit patterns on the wafer. Amanufacturing apparatus used in each step undergoes maintenance by theremote maintenance system, which prevents a trouble in advance. Even ifa trouble occurs, the manufacturing apparatus can be quickly recovered.The productivity of the semiconductor device can be increased incomparison with the prior art.

[0082] As has been described above, the present invention can alwaysexpose a wafer to a circuit pattern with high precision withoutdecreasing the productivity of an exposure apparatus which uses a laseroscillation apparatus as a light source.

[0083] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. A laser oscillation apparatus comprisingwavelength change means for driving a wavelength selection element andchanging an oscillation wavelength of a laser beam to a target value,wherein said wavelength change means calculates a driving amount of thewavelength selection element on the basis of the target value, drivesthe wavelength selection element on the basis of the calculated drivingamount of the wavelength selection element, and changes the oscillationwavelength of the laser beam to the target value.
 2. The apparatusaccording to claim 1 , wherein the apparatus further comprisesoscillation history memory means for storing an oscillation state of thelaser beam as an oscillation history, and said wavelength change meanscalculates the driving amount of the wavelength selection element on thebasis of the oscillation history, drives the wavelength selectionelement on the basis of the calculated driving amount of the wavelengthselection element, and changes the oscillation wavelength of the laserbeam to the target value.
 3. The apparatus according to claim 2 ,wherein the oscillation history includes at least one of an oscillationwavelength change amount of the laser beam, an oscillation idle time ofthe laser beam, and an oscillation duty.
 4. The apparatus according toclaim 1 , wherein thresholds are set for the oscillation wavelengthchange amount of the laser beam and the oscillation idle time of thelaser beam, whether the oscillation wavelength change amount of thelaser beam or the oscillation idle time of the laser beam exceeds thethreshold is determined, and a wavelength lock signal is output based ona determination result.
 5. The apparatus according to claim 4 , whereina shutter is closed when the oscillation wavelength change amount of thelaser beam or the oscillation idle time of the laser beam exceeds thethreshold.
 6. The apparatus according to claim 1 , further comprisingwavelength measurement means for measuring the oscillation wavelength ofthe laser beam.
 7. The apparatus according to claim 6 , wherein theapparatus further comprises internal environment measurement means formeasuring an internal environment of said wavelength measurement means,and said wavelength measurement means is corrected based on the measuredinternal environment of said wavelength measurement means.
 8. Theapparatus according to claim 7 , wherein the internal environment ofsaid wavelength measurement means includes at least one of a temperatureand atmospheric pressure.
 9. The apparatus according to claim 6 ,wherein whether the measured oscillation wavelength of the laser beamfalls within a predetermined allowable range is determined, and awavelength lock signal is output based on a determination result. 10.The apparatus according to claim 9 , wherein output of the laser beam isstopped when the oscillation wavelength of the laser beam does not fallwithin the predetermined allowable range.
 11. The apparatus according toclaim 1 , wherein output of the laser beam is not stopped in changingthe oscillation wavelength of the laser beam.
 12. The apparatusaccording to claim 1 , wherein no test laser beam is emitted in changingthe oscillation wavelength of the laser beam.
 13. The apparatusaccording to claim 1 , wherein the wavelength selection element includesone of a grating and etalon.
 14. The apparatus according to claim 1 ,wherein the laser beam includes an excimer laser beam.
 15. An exposureapparatus using a laser oscillation apparatus as a light source, whereinthe laser oscillation apparatus comprises wavelength change means fordriving a wavelength selection element and changing an oscillationwavelength of a laser beam to a target value, and said wavelength changemeans calculates a driving amount of the wavelength selection element onthe basis of the target value, drives the wavelength selection elementon the basis of the calculated driving amount of the wavelengthselection element, and changes the oscillation wavelength of the laserbeam to the target value.
 16. The apparatus according to claim 15 ,wherein the oscillation wavelength of the laser beam is changed betweenend of exposure in a predetermined exposure region on a substrate to beexposed and start of exposure in a next exposure region.
 17. Asemiconductor device manufacturing method of manufacturing asemiconductor device by using an exposure apparatus, comprising thesteps of: applying a resist to a substrate; drawing a pattern on thesubstrate by using the exposure apparatus; and developing the substrate,wherein the exposure apparatus uses as a light source a laseroscillation apparatus having wavelength change means for driving awavelength selection element and changing an oscillation wavelength of alaser beam to a target value, and the wavelength change means calculatesa driving amount of the wavelength selection element on the basis of thetarget value, drives the wavelength selection element on the basis ofthe calculated driving amount of the wavelength selection element, andchanges the oscillation wavelength of the laser beam to the targetvalue.
 18. A semiconductor device manufacturing method comprising thesteps of: installing manufacturing apparatuses for various processesincluding an exposure apparatus in a semiconductor manufacturingfactory; and manufacturing a semiconductor device by using themanufacturing apparatuses in a plurality of processes, wherein theexposure apparatus uses as a light source a laser oscillation apparatushaving wavelength change means for driving a wavelength selectionelement and changing an oscillation wavelength of a laser beam to atarget value, and the wavelength change means calculates a drivingamount of the wavelength selection element on the basis of the targetvalue, drives the wavelength selection element on the basis of thecalculated driving amount of the wavelength selection element, andchanges the oscillation wavelength of the laser beam to the targetvalue.
 19. The method according to claim 18 , further comprising thesteps of: connecting the manufacturing apparatuses by a local areanetwork; and communicating information about at least one of themanufacturing apparatuses between the local area network and an externalnetwork outside the semiconductor manufacturing factory.
 20. The methodaccording to claim 19 , wherein a database provided by a vendor or userof the exposure apparatus is accessed via the external network to obtainmaintenance information of the manufacturing apparatus by datacommunication, or production management is performed by datacommunication between the semiconductor manufacturing factory andanother semiconductor manufacturing factory via the external network.21. A semiconductor manufacturing factory comprising: manufacturingapparatuses for various processes including an exposure apparatus; alocal area network for connecting said manufacturing apparatuses; and agateway which allows the local area network to access an externalnetwork outside the factory, wherein information about at least one ofsaid manufacturing apparatuses can be communicated, said exposureapparatus uses as a light source a laser oscillation apparatus havingwavelength change means for driving a wavelength selection element andchanging an oscillation wavelength of a laser beam to a target value,and said wavelength change means calculates a driving amount of thewavelength selection element on the basis of the target value, drivesthe wavelength selection element on the basis of the calculated drivingamount of the wavelength selection element, and changes the oscillationwavelength of the laser beam to the target value.
 22. A maintenancemethod for an exposure apparatus installed in a semiconductormanufacturing factory, comprising the steps of: causing a vendor or userof the exposure apparatus to provide a maintenance database connected toan external network of the semiconductor manufacturing factory;authorizing access from the semiconductor manufacturing factory to themaintenance database via the external network; and transmittingmaintenance information accumulated in the maintenance database to thesemiconductor manufacturing factory via the external network, whereinthe exposure apparatus uses as a light source a laser oscillationapparatus having wavelength change means for driving a wavelengthselection element and changing an oscillation wavelength of a laser beamto a target value, and the wavelength change means calculates a drivingamount of the wavelength selection element on the basis of the targetvalue, drives the wavelength selection element on the basis of thecalculated driving amount of the wavelength selection element, andchanges the oscillation wavelength of the laser beam to the targetvalue.
 23. The apparatus according to claim 15 , wherein the exposureapparatus further comprises a display, a network interface, and acomputer for executing network software, and maintenance information ofthe exposure apparatus can be communicated via the computer network. 24.The apparatus according to claim 23 , characterized in that the networksoftware is connected to an external network of a factory where theexposure apparatus is installed, provides on said display a userinterface for accessing a maintenance database provided by a vendor oruser of the exposure apparatus, and enables obtaining information fromthe database via the external network.